Low temperature zoning formation system for holding freshness of food

ABSTRACT

A low temperature zone forming system by convection type thermal stratification in which the low temperature zone separated from polluted outside air is formed on a movable or fixed table for handling commodities such as marine products while maintaining freshness thereof during the period from carrying-in in the whole sale market, during selling by auction, until shipment of the commodities from the market, comprising an upward-open case body ( 30 ) mounted on a chassis ( 30   a ), a separate brine chilling unit ( 30   b ), and a brine piping ( 30   c ), the upward-open case body ( 30 ) further comprising a roller conveyer ( 35 ) installed in the center part of the floor of the case body ( 30 ), cooling flat plates each of which is installed adjacent to the roller conveyer ( 35 ), and cooling flat plates are installed on the inside faces of both laterally longitudinal side walls.

TECHNICAL FIELD

The present invention relates to a low temperature zone forming systemrequired not only in a food processing factory such as a meat and marineproducts processing factory but also for the transport and temporalstorage of foodstuffs in a whole sale market of marine products, fruitsand vegetables, etc., specifically to a low temperature zone formingsystem to maintain freshness of food such as marine products by forminga low temperature zone on a portable or fixed table used in a whole salemarket where food such as marine products, etc. are handled and where itis necessary to maintain freshness of said marine products aftercarrying-in in the market, during auction in the market, and untilforwarding form the market.

BACKGROUND ART

At the auction in a marine products wholesale market, for example in afish market where fishes are landed from fisher boats, the landed fishesare sorted, cleaned, and arranged directly on the floor of the auctionmarket in a heap of about 40 cm square separately according to fisherboats landed the fishes and to the kind of fish to prepare for auction.Auction site extends to about 300 m long, considerable time is neededuntil the last auction finishes, and there have been problems of dryingand rising in temperature of fishes caused by being exposed to wind andsunlight.

In a whole sale market, collection, sorting, storing, trading,transportation, and disposal of fresh marine products are done in ashort time, during which nearly all or all of the fresh marine productsare exposed to outside air and transferred from owners to buyers. Duringthat time period, the fresh marine products are exposed to an atmospherecontaminated with exhaust gases, bacteria, etc. It is desiredparticularly in the case of trading fresh marine products that tradingis done in a state the fresh marine products are accommodated in a lowtemperature zone separated from said contaminated atmosphere. That is, alow temperature storage facility is required in a whole sale market forthe purpose of hygiene and maintaining freshness of the products.

As to such a low temperature zone forming system as mentioned above,there have not been disclosed much proposals directly applicable to suchsituation. A proposal relating to a refrigerating apparatus in which acold air curtain is formed across the opening of the apparatus wasdisclosed, for example, in Japanese Laid-Open Utility Model ApplicationNo. 01-28778.

The proposal relates to a refrigerating apparatus in which an aircurtain is formed across the opening through which commodities aregotten in and out of the apparatus.

The apparatus is composed as shown in FIG. 9. A show case body 51 has astorage room 52 for accommodating commodities and an opening 53 isprovided for getting the commodities in and out of the storage room. Onboth sides of the opening 53 are formed an air admission port 55 forsucking in cold airflow 54 and an air outlet port 56 to blowing out coldairflow 54, both the ports opposing to each other.

In the passage 57 under the bottom of the storage room 52 communicatingthe air admission port 55 with the air outlet port 56 are located ablower 58 for forcing circulation air, an evaporator 60 for cooling thecirculation air in an ordinary operation, and a heat exchanger 59 forcooling the circulation air when defrosting the evaporator. In a baseframe 61 are located a condenser 62 and compressor 63 of a refrigeratingmachine.

In an ordinary operation, refrigerant circulates from the compressor 63through the condenser 62, heat exchanger 59, expansion valve not shownin the drawing, and evaporator 60 where the circulation air is cooled bythe evaporation of the refrigerant, to be returned to the compressor 63.The high-pressure, high-temperature refrigerant gas compressed in thecompressor 63 is cooled in the condenser 62 to be condensed to a liquidstate, the liquid refrigerant is supercooled in the heat exchanger 59and then expanded through the expansion valve to be evaporated in theevaporator 60 to cool the circulation air.

When defrosting the evaporator, the refrigerant is circulated from thecompressor 63 through the condenser 62, evaporator 60, and heatexchanger 59 to be returned to the compressor 63. The evaporator 60 isdefrosted by the sensible heat of the liquid refrigerant from thecondenser 62. The liquid refrigerant supercooled through the defrostingprocess flows by way of an expansion valve not shown in the drawing tothe heat exchanger 59 where it evaporates and cools the circulation air.

According to the proposal, as defrosting operation is possible byinverting the direction of the refrigerant circulation in an ordinaryoperation and the defrosting operation is done while the coolingcirculation air is done, the rise in temperature in the storage roomduring defrosting is prevented. As an air curtain is formed across theopening of the storage room, the apparatus can maintain freshness offresh marine products accommodated in the storage room.

Besides said proposal, a proposal relating to belt conveyer equipmentfor transferring cold food used to transfer and dispose foodstuffs andfood articles in food processing factories such as meat, marine productsprocessing factories, etc. was disclosed recently, for example, inJapanese Laid-Open Patent Application No. 11-287545. The equipment iscomposed as shown in FIG. 10. Cold air blow out openings 74 a andadmission openings 74 b opposing to each other across the belt conveyer72 are provided on both left and right sides along the transferdirection S of a belt conveyer 72 for transferring cold food, and coldspace R is produced on the belt by the cold air.

A cooling section 75 is provided in the space between the upper,transfer side belt 72 a and lower, return side belt 72 b of the beltconveyer 72. Cold air cooled in the cooling section is sent to the coldair blow out openings 74 a to be blown out onto the surface of thetransfer side belt 72 a and sucked from the admission openings 74 b,thus the cold air is circulated.

With the composition mentioned above, cold space R is produced on thesurface of the transfer side belt 72 a and at the same time the rearside thereof is also cooled.

The above proposal can be applied to a low temperature zone formingsystem required not only in a food processing factory such as a meat,marine products processing factory but also for transferring andtemporally storing foodstuffs in a wholesale market of marine productsor fruits and vegetables.

As to a low temperature forming system in which an atmosphere of lowtemperature shielded from an outside contaminated atmosphere is formed,there has been no proposal directly applicable to the situationconcerned. Proposals of heat storage tank in which heat is stored in athermally stratified state have been disclosed hitherto. An example ofsuch a proposal uses a thermal stratification type heat storage tank inwhich the difference in density of water depending on the temperaturesthereof is utilized to store water in a stratified state withoutallowing hot water lower in density to mix with cold water high indensity.

Besides said proposal, an apparatus and method for displaying andstoring hauled fishes was disclosed in Japanese Laid-Open PatentPublication No. 2000-14315, in which hygiene and quality problemsinduced by the auction of hauled fishes arranged on the floor of themarket was solved and hygienic storage of hauled fishes was madepossible.

The display and storage apparatus is composed, as shown in FIG. 11, of acooling part which is a cooling panel 78 a with a brine passage 78 bformed inside thereof and an insulation part 79 attached to the bottomthereof, hauled fishes being possible to be displayed on the surface ofthe cooling panel. Brine usable for food is supplied to the brinepassage to cool the cooling panel. The apparatus is provided in a fishmarket and the distribution process is carried out on the display andstorage apparatus.

As can be seen in the proposals mentioned above, it is required in amarket that, a space formed into a box shape which can be moved asnecessary is provided as a commodity storage facility, and the outsideair including warm air in the space is driven out and instead cold airis supplied into the space to speedily replace the atmosphere inside thespace by an cold atmosphere of uniform temperature distribution.

As a method of the displacement, there has been known a method offorming a fresh air zone in the lower part of a room near the floorwhere people reside or work by utilizing the thermal stratification ofair caused by the temperature difference between the temperature of theair-conditioned air supplied to the room and that of the warm air heatedby the heat generated in the room. As such was disclosed in JapaneseLaid-Open Patent Application No. 06-185780 a method and apparatus forventilation. According to the proposal, as shown in FIG. 12,air-conditioned air 82 lower in temperature than the temperature of theair inside the room 80 is blown out at low speed from a ventilation airoutlet 81 located near the floor of the room 80, and nozzles are locatednear the ceiling for producing high speed air jet streams 83 to allowthe air in the room near the ceiling to be ejected accompanied with theair jet streams through an exhaust opening located near the ceiling.Thus, ventilation can be performed efficiently.

However, with the prior art disclosed in said Japanese Laid-Open UtilityModel Application No. 01-28778, there is a problem that the surfaces ofthe commodities dry out, for cold air for forming the air curtainstrikes the accommodated commodities such as marine products.

Further, there is also a problem that cleaning is vexatious andaccompanies difficulty because the air admission port, air outlet port,fan, etc. are located in the rear side of the cold storage room foraccommodating marine products as commodities.

Further, the proposal is related to the utilization of an air curtain ofcold air for shielding the cold storage room from outside atmosphere andthere is no description about maintaining the storage room in lowtemperature.

Further, as the apparatus includes a cold air circulation mechanism (aheat exchanger, fan, air admission port, and air outlet port), the spacefor displaying commodities is limited and there is a problem that itaccompanies difficulty to place the apparatuses to match the structureand availability of a market.

The prior art disclosed in said Japanese Laid-Open Patent ApplicationNo. 11-287545 is composed such that a cold space is formed on a beltconveyer for transferring processed cold food article by blowing coldair, and there is a problem similar to that which exists in saidJapanese Laid-Open Utility Model Application No. 01-28778.

The prior art disclosed in said Japanese Laid-Open Patent ApplicationNo. 2000-14315 is related to low temperature storage using a coolingpanel. The panel is used only for placing marine products such as hauledfishes thereon and there is no description about efficiently forming alow temperature zone around the hauled fishes placed on the panel.

The prior art disclosed in said Japanese Laid-Open Patent ApplicationNo. 06-185780 is related to the displacement of the air inside a roomutilizing a well-known method of thermal stratification and not relatedto the formation of a low temperature zone for storing fresh foodstuffssuch as marine products.

By the way, as mentioned before, low temperature storage facilities forthe purpose of sanitation and maintaining freshness of foodstuffs arerequired in central whole sale markets handling mainly marine products,fruits and vegetables and prefabricated refrigerators or low temperatureforming facilities are beginning to be provided there recently.

A displaying facility of hauled fishes capable of being removed easily,not a permanent facility, was proposed by the applicants of the presentapplication and others.

Said proposal relates to a displaying and storing equipment to surroundan auction market and fill the surrounded space with cold air.

The cooling system of the proposal for forming a cold zone is an opentype, local cooling system in which the cold air is not recovered, andthere is room for improvement. On the other hand, need for a lowtemperature storage facility is increasing and a low cost, compact, andhighly efficient facility is desired.

Currently, the handling operation of fresh foodstuffs such as marineproducts from arrival to shipment in a market is done under ordinarytemperature in many cases, and improvement from the viewpoint of hygieneand maintaining freshness is strongly demanded.

Presently, as to lowering the temperature in an auction market, thereare attempts to include a whole auction market in a large box typefacility, but in this case the reception of goods, prearrangement forauction, preliminary inspection, and shipment must be carried out underlow temperature for a long time period and there arises a problem ofmaintenance of good health of workers working under a low temperatureatmosphere.

DISCLOSURE OF THE INVENTION

The present invention is made in light of the problems mentioned above,and the object is to provide a low temperature zone forming system formaintaining freshness of foodstuffs in which a low temperature zoneseparated from a contaminated atmosphere is formed on a movable or fixedtable. By applying the system to a wholesale market handling mainlyfresh foodstuffs, carrying-in of the fresh foodstuffs in the whole salemarket, auctioning, and shipment thereof can be performed whilemaintaining freshness thereof.

-   {circle around (1)} The present invention proposes a low temperature    zone forming system including an upward-open case body for    displaying commodities, the case body confining a space surrounded    with the floor face and four side walls, to be used for maintaining    freshness of fresh marine products in a whole sale market,    characterized in that a thermally stratified low temperature zone    having temperature distribution in a vertical direction is formed    above said floor face.

In the invention, a concept of thermal stratification is introduced inthe boxed space of an upward-open case body to be used in an auctionmarket for displaying fresh foodstuffs such as marine products(hereafter referred to as commodities). A low temperature zone havingtemperature distribution in a vertical direction is formed above thefloor of the upward-open case body surrounded with four side walls, andsaid commodities are displayed in the low temperature zone. By theformation of said thermally stratified low temperature zone, themovement of the cold air in the low temperature zone is interrupted bythe warm air region in the upper part of the low temperature zone, andthe low temperature can be maintained efficiently without beingdispersed outward, so that the marine products is accommodated in analmost stationary low temperature space without the movement of air andthe problem of damage in the quality of foodstuffs does not occur. Theproblem of contamination of foodstuffs by outside air is also prevented,for the contaminated air in the warm region consisting of outside air isshut off from entering the low temperature zone under the warm region.

-   {circle around (2)} It is preferable that cold air is introduced in    the lower part of said low temperature zone.

The above invention is related to the cold-air introduction typethermally stratified low temperature zone which is formed by introducingcold air from outside into the low temperature zone formed above thefloor of the boxed space.

The condition of the low temperature zone is different depending on theintroduction velocity of cold air. When cold air is introduced at a lowvelocity, the vertical temperature distribution in the low temperaturezone is not influenced largely by the introduction of cold air andreplacement of the cold air zone occurs under soft convection. When thevelocity is large, formation of a new cold air zone occurs.

By the way, when outside air is cooled and directly introduced, it isrequired to filtrate the air.

The introduction of said filtered cold air from outside is necessary forthe system to comply with a change in temperature or contamination ofthe air in the low temperature zone caused by carrying-in and -out orreplacing commodities.

-   {circle around (3)} It is preferable that said cold air is    introduced at low velocity in an ordinary operation and the    introduction of cold air is switched to a forced introduction to    form a stratified low temperature zone having a required temperature    distribution in a vertical direction as necessary.

The above invention is related to the system composition for forciblyforming a low temperature zone consisting of a new temperature zonethrough forced introduction of cold air into the low temperature zone.

-   {circle around (4)} It is preferable that said floor is a heat    exchanger having heat transfer faces on both sides thereof, one of    the heat transfer faces forming a cooling floor face and the other    of the heat transfer faces forming a heat transfer face to perform    heat exchange in the cold air producing chamber formed in the rear    face side of the floor, the warm air in the warm air zone in the    upside opening region of said case body is introduced into said cold    air producing chamber to be cooled therein, and the cold air    produced in the chamber is introduced into the low temperature zone    formed above said one of the heat transfer faces to form a new cold    air stratified zone.

The above invention is related to a means for forming a low temperaturezone in the boxed space of the upward-open case body surrounded by thefloor and four side walls by the cold air introduction type thermalstratification according to the present invention. A cooling heatexchanger having a heat transfer face on both sides for cooling air isprovided all over the floor face of the upward-open case body, one ofthe heat transfer face cools the air in the boxed space, the other heattransfer face cools the air in the cold air producing chamber formedunder the floor, the warm air in the warm air region in the upper partof the low temperature zone is introduced into the cold air producingchamber to produce the cold air to be introduced to the low temperaturezone to replace the air therein. It is preferable to filter the warm airto be introduced into the cold air production chamber before introducedthereinto.

-   {circle around (5)} It is preferable that said floor is a cooling    flat plate having heat transfer faces on both sides thereof, one of    the heat transfer faces forming a cooling floor face and the other    of the heat transfer faces forming a heat transfer face to perform    heat exchange in the cold air producing chamber formed in the rear    face side of the floor, the warm air in the warm air zone in the    upside opening region of said case body is introduced into said cold    air producing chamber to be cooled therein, and the cold air    produced in the chamber is introduced into the low temperature zone    formed above said one of the heat transfer faces to form a new cold    air stratified zone.

In the above invention, a cooling flat plate having heat transfer faceson both sides thereof is used instead of said heat exchanger.

-   {circle around (6)} It is preferable that a separate cooling panel    is attached to the rear face of said floor, the cold air produced by    means of the panel is forced into the low temperature zone above the    floor to form a cold air stratified zone of required temperature.

The above invention is related to a means for forming a low temperaturezone by the cold air introducing type thermal stratification capable ofcomplying with forced cold-air introduction. By forcibly introducing theair cooled by the cooling panel installed on the rear face of the floor,whole of the low temperature zone is cooled and a new cold air zone canbe formed in a short time to be able to comply with forced cold-airintroduction.

-   {circle around (7)} It is preferable that said floor is a    one-side-cooling flat plate having a flat heat transfer face on one    side thereof, and the formation of the thermal stratification is    possible in a short time period by concentrating cooling capacity to    said heat transfer face.

In the above invention, a one-side-cooling flat plate having a flat heattransfer face on one side thereof is used instead of said heatexchanger. This is effectively used when forming a space for displayingcommodities speedily in a wholesale market, etc.

-   {circle around (8)} It is preferable that the inside face of said    four side walls and said floor face are composed to be cooling flat    plates, so that convection type cold air stratified zone is formed    by the low temperature zone formed by the convection between the    descending cold air current produced due to the cooling of air by    the cooling plates of the four side walls and the cold air zone    produced due to the cooling of air by the cooling plates of the    floor and the hot air region formed above said low temperature zone.

The above invention is related to a low temperature forming byconvection type thermal stratification, which is anther type of lowtemperature zone formation different from the cold air introduction typelow temperature zone forming.

In the low temperature zone formation by convention type thermalstratification, the low temperature zone is formed not only by the useof the cooling plate installed on the floor face but also of the coolingflat plates installed on the inside faces of the four side walls.

In this case, descending cold air current occurs along the cooling flatplates installed on the inside faces of the side walls, naturalconvection is induced by said air current and the cold air stratifiedzone formed on the floor face, and a low temperature zone having a thickcold air zone can be formed.

-   {circle around (9)} It is preferable that cooling flat plates are    provided on the inside faces of laterally longitudinal walls among    the four side walls.-   {circle around (10)} It is preferable that a transfer section    consisting of a roller conveyer is provided on a part of said floor    in a laterally longitudinal direction or in a crosswise direction,    and cooling flat plate or plates which can serve as chopping boards    are provided in a position or positions other than the transfer    section.

The above invention is related to the composition of the floor of theboxed space. A roller conveyer is installed on part of the rectangularfloor in a longitudinal direction or crosswise direction and coolingflat plate or plates which serve as chopping boards are provided in aposition or positions other than the transfer section. By this, theefficiency of carrying-in and -out of commodities to be displayed orcommodities displayed is promoted and cross contamination by handhandling is reduced, and cooling flat plate or plates are providedadjacent to the roller conveyer which can serve as chopping boards. Byusing the cooling plate as a chopping board, the commodities can be cutas necessary before auctioning.

-   {circle around (11)} It is preferable that the roller conveyer is    provided on said floor in a laterally longitudinal direction.-   {circle around (12)} It is preferable that said four side walls can    be turned over outward or detached, and when storing commodities in    the case body, the walls are recovered to an erect state with the    walls closely contacted with the floor to be able to again allow the    formation of the low temperature zone.

The above invention is related to the structure of the side walls of theupward-open case body for forming a low temperature zone. The efficiencyof cleaning is promoted by composing so that the walls can be turnedover outward through connecting the lower ends of the walls by pivots orthe walls are detachable in order to allow commodities to be carried-inor -out.

It is suitable to compose so that the side walls perpendicular to theroller conveyer can be detached. By this, when a plurality of the casebody are connected with said side walls detached, the roller conveyer ofeach of the case bodies can be brought into communication with eachother, and a long low temperature zone of which the length can beadjusted in accordance with market conditions and space. Further, byinstalling said roller conveyer, the transfer of heavy marine productsbecomes easy and the efficiency of auction is promoted.

-   {circle around (13)} It is preferable that the temperature of said    low temperature zone can be controlled in a temperature range from    storage temperature with ice to a temperature for maintaining frozen    state of marine products by adjusting cooling temperature of the    cooling heat exchanger or cooling flat plate through controlling the    temperature of the heat sink for cooling the heat exchanger or the    cooling flat plates.

The above invention is related to a setting means of the temperature ofthe low temperature zone. The system is composed so that the temperatureof the low temperature zone can be controlled in accordance with thecommodities handled in the auction market. It is suitable that thetemperature can be controlled in the temperature zone used for lowtemperature storage of foodstuffs. For example, it is suitable to makeit possible to control the temperature to maintain a low temperature ofchilling zone, i.e. lower than contact icing temperature of about 3° C.,which is the toxin producing limit temperature of batulinus and breedinglimit temperature of erwinieae, including the temperature formaintaining frozen state of the frozen foodstuffs.

-   {circle around (14)} It is preferable that current plates are    provided at the opening for introduction of cold air to the low    temperature zone.

The above invention is related to the composition of the opening forinducing cold air into the low temperature zone formed in theupward-open case body. It is suitable to provide current plates toprevent the cold air from being introduced in a turbulent state.

-   {circle around (15)} It is preferable that a cold air producing    chamber which is a shallow passage formed under the cooling heat    exchanger or cooling flat plate of which one of the heat transfer    faces forms said floor face and the other heat transfer face forms    the rear face of the floor, and said rear side heat transfer face is    provided with concavities and convexities, fins, or is blast    finished.

The above invention is related to the configuration of the cold airproducing chamber below the rear side heat transfer face of the coolingheat exchanger or cooling flat plate forming the floor of theupward-open case body. It is suitable to form the cold air producingchamber such that the cross section thereof is thin to form a narrowpassage in order to raise the velocity of air flowing in the passage andraise heat transfer efficiency between the air flow and the heattransfer face. The heat transfer face is suitable to be provided withconcavities and convexities, fins, or is blast finished.

-   {circle around (16)} It is preferable that said cooling heat    exchanger or cooling flat plate provided to said floor face or to    both of said floor face and inside faces of walls are supplied with    the brine cooled by the refrigerating machine which is housed in the    space under the floor of the upward-open case body or the brine    cooled by a central refrigerating machine which is located outside    the system by means of brine piping.-   {circle around (17)} It is preferable that a shut-off valve is    attached to the connector fixed to the end of each brine piping    which is integrated in said cooling heat exchanger or cooling flat    plates installed on said floor face or on both of the floor face and    the inside faces of said side walls in order that the leakage of    brine is prevented when detaching or attaching said cooling flat    plates.

The above invention is related -to the connection between a heat sinkapparatus and the cooling heat exchanger or cooling flat plate formingthe floor and the cooling flat plates installed on the four side wallsof the upward-open case body for forming a low temperature zone.Propylene or salt water is used as a cooling medium. As the heat sinkapparatus, a brine cooler is accommodated in the lower part of the casebody or a refrigerating unit is provided separately. The heat exchangerand cooling flat plates are connected to the brine piping by mean oftouch connectors such as couplers. Automatic shut-off valves areprovided to the heat exchanger and cooling flat plates, the brineremains in the heat exchanger and cooling flat plates even after theyare detached, and the leakage of brine is prevented.

-   {circle around (18)} It is preferable that said upward-open case    body is provided with a sunshade sheet to prevent sunlight streams    into the low temperature zone.-   {circle around (19)} It is preferable that said upward-open case    body is provided with casters or the like at its foot parts, and the    vertical position of the floor of the case body is such that    putting-on and -down of commodities is easily possible.

It is suitable to attach casters at the foot parts of the upward-opencase body for forming a low temperature zone for displaying commoditiesto make the case body movable. In the case of a cold air introductiontype low temperature forming system which is applied for displayingmainly small-sized marine products, it is suitable to compose such thatthe floor of the case body is positioned at the height corresponding toworker's waist-height to promote the efficiency of loading work.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an embodiment of a low temperaturezone forming system capable of complying with forced cold-aircirculation according to the present invention in which the lowtemperature zone is formed by introducing cold air.

FIG. 2(A) is a schematic block diagram showing when parallel operationof a plurality of the low temperature forming systems of FIG. 1 isperformed by use of a brine cooler, and FIG. 2(B) is an illustrationshowing when marine products for display are carried-in in the lowtemperature forming system of FIG. 1.

FIG. 3 is an illustration showing a basic pattern of convection in thelow temperature zone forming system of the present invention in whichthe low temperature zone is formed by convection.

FIG. 4(A), FIG. 4(B), and FIG. 4(C) are respectively a top plan view, afront elevation, and a side elevation with partially sectional view ofthe low temperature zone forming system of which the basic pattern ofconvection is shown in FIG. 3.

FIG. 5(A) is a perspective view when a single unit of the lowtemperature zone forming system of FIG. 4 is operated, and FIG. 5(B) aplurality of the low temperature zone forming system of FIG. 4 areconnected.

FIG. 6 is a graph showing a cooling test result of changes intemperatures over time at positions different in height from the surfaceof the table in the low temperature zone forming system of FIG. 4.

FIG. 7 is a graph showing the distribution of temperatures in ahorizontal direction at positions different in height from the surfaceof the table after 1.5 hours from the start of the cooling test of FIG.6.

FIG. 8 is a graph showing the distribution of temperatures in a verticaldirection in the cooling test of FIG. 6.

FIG. 9 is a schematic illustration of a prior art refrigeratingapparatus in which a cold air curtain is formed across the opening ofthe apparatus.

FIG. 10 is a schematic illustration of prior art belt conveyer equipmentfor transferring cold food.

FIG. 11 is a schematic illustration of a prior art marine productsdisplaying apparatus.

FIG. 12 is a schematic illustration of a prior art ventilation apparatusutilizing thermal stratification for replacing the air in a room.

BEST MODE FOR EMBODIMENT OF THE INVENTION

A preferred embodiment of the present invention will now be detailedwith reference to the accompanying drawings. It is intended, however,that unless particularly specified, dimensions, materials, relativepositions and so forth of the constituent parts in the embodiments shallbe interpreted as illustrative only not as limitative of the scope ofthe present invention.

FIG. 1 is a schematic illustration of an embodiment of a low temperaturezone forming system capable of complying with forced cold-aircirculation in which the low temperature zone is formed by introducingcold air, FIG. 2(A) is a schematic block diagram showing when paralleloperation of a plurality of the low temperature forming systems of FIG.1 is performed by use of a brine cooler, and FIG. 2(B) is anillustration showing when marine products for display are carried-in inthe low temperature forming system of FIG. 1. FIG. 3 is an illustrationshowing a basic pattern of convection in the low temperature zoneforming system in which the low temperature zone is formed byconvection. FIG. 4(A), FIG. 4(B), and FIG. 4(C) are respectively a topplan view, a front elevation, and a side elevation with partiallysectional view of the low temperature zone forming system of which thebasic pattern of convection is shown in FIG. 3. FIG. 5(A) is aperspective view when a single unit of the low temperature zone formingsystem of FIG. 4 is operated, and FIG. 5(B) a plurality of the lowtemperature zone forming system of FIG. 4 are connected.

FIG. 6 is a graph showing a cooling test result of changes intemperatures over time at positions different in height from the surfaceof the table in the low temperature zone forming system of FIG. 4, FIG.7 is a graph showing the distribution of temperatures in a horizontaldirection at positions different in height from the surface of the tableafter 1.5 hours from the start of the cooling test, FIG. 8 is a graphshowing the distribution of temperatures in a vertical direction.

Referring to FIG. 1, a low temperature zone forming system 25 of thepresent invention capable of complying with forced cold-air circulationis composed such that a low temperature zone is formed in the uppersection of a high deck structure 20 having casters 20 a. An upward-opencase body 10 is provided on the structure, height H from the floor ofthe market to the bottom floor of the case body 10 being determined suchthat carrying-in and -out of commodities in the low temperature zone ispossible in order to make it easy for workers to carry-in and -outcommodities. The case body 10 has inner four side walls 13 a and outerfour side walls 13. A low temperature zone 15 capable of complying withforced cold-air circulation is formed in the space above the surface 11a of a heat transfer face 11 serving as the bottom floor of the casebody 13 surrounded by said inner walls. The low temperature zone 15 isseparated from outside air by a warm air zone 16 of temperature higherthan that of the low temperature zone 15 and about equal to that ofoutside air, reference numeral 17 showing a horizontal boundary of bothzones.

Commodities such as marine products are displayed in the low temperaturezone 15 to be maintained in a low temperature for auctioning. Whenreplacing commodities or starting operation of the system, cold air isforced into the low temperature zone 15 to form a low temperature withnewly introduced cold air.

Said heat transfer face 11 a of the floor serves as an upper heattransfer face of the cooling flat plate 11 to cool the air staying onthe floor for forming the low temperature zone 15. A cold air producingchamber 12 is formed below the lower heat transfer face 11 b of thecooling flat plate 11, the chamber 12 being an air passage shallow inits depth, the air passing through the passage being cooled by the heattransfer face 11 b. An admission opening 18 a communicating to the warmair zone 16 is provided in the right side of the low temperature zone15, and a fan 18 of variable rotation speed is provided in the passagecommunicating the opening 18 a with the cold air producing chamber 12.In the left side of the low temperature zone 15 is formed an opening tointroduce the cold air produced in the chamber 12 into the lowtemperature zone 15, current plates 19 being provided at the opening.

Forced cold-air circulation operation is performed by sucking air fromthe warm air zone 16 with high velocity by means of the variable speedfan 18, the warm air sucked by the fan 18 is introduced into the coldair producing chamber 12 to be cooled, and the cooled air is introducedinto the low temperature zone 15 passing through the current plates 19through which the air flow is straightened to cool speedily the wholelow temperature space by replacing the air in the space speedily.

The air passage constituting the cold air producing chamber 12 is formedto be shallow in depth in order to achieve efficient heat transfer fromthe lower side heat transfer face 11 b, and the face 11 b is providedwith concavities and convexities, fins, or is blast finished to improveheat transfer.

When said forced introduction of cold air and replacement of commoditiesis finished, said fan 18 is switched to low speed operation and cold airis introduced into the low temperature zone at low speed.

Propylene glycol or salt water is used for the brine to cool saidcooling flat plate 11 for the sake of food safety, and the brine iscooled by a refrigerating machine 21 accommodated under the case body orby a separate brine cooler 21 a as shown in FIG. 2(A). A plurality ofthe forced cold-air circulation type low temperature zone forming system25 can be connected by means of brine piping 21 b to perform paralleloperation.

The laterally longitudinal walls 22 of the low temperature zone formingsystem 25 can be turned over in the direction shown by arrow A in FIG.2(B) in order that commodities can be easily carried-in onto or put downfrom the floor formed by the cooling flat plate 11 positioned at theheight corresponding to worker's waist-height.

In FIG. 3 is shown a basic pattern of convection in the low temperaturezone forming system of the present invention in which the lowtemperature zone is formed by convection. As can be seen in FIG. 3, theconvection type low temperature zone 43 is formed in the inside space ofan upward-open case body 40 placed on the movable or fixed tableprovided in a wholesale market or on the floor of the market, a coolingflat plate 31 a forming the bottom floor of the space in the case body40. Warm air region 44 consisting of outside air is separated through anintermediary horizontal boundary 44 a, and the low temperature zone 43is formed by natural convention 45 above said cooling flat plate 31 a.The low temperature zone 43 is maintained in a temperature between thecontact icing temperature lower than 3° C., which is most suitable formaintaining freshness of marine products, and the temperature necessaryto maintain frozen state.

Said low temperature zone 43 is formed by convection between the warmair region 44 formed above the horizontal boundary 44 a and the lowtemperature zone 43 as follows.

A cooling flat plate 31 a, 33 a, and 33 b are installed on the floorface and inside faces of walls of the case body 40 respectively, andbrine is circulated inside these cooling plates as a cooling medium tomaintain the temperature of the cooling surface to a temperature zonenear 0° C.˜−20° C.

Air layer of temperature lower than that of outside air and higher indensity than that of outside air is formed on the faces of the coolingplates 33 a and 33 b of the side walls, the cooled air flows down slowlyto cause natural convection 45 without involving the warm air of lowerdensity in the warm air region. Thus, the convection occurs between thewarm air region 44 separated by the boundary 44 a and the lowtemperature zone 43 resulting in the formation of the low temperaturezone by convection.

With the composition mentioned above, the low temperature zone 43 isformed without involving polluted outside air, and freshness of thecommodities placed on the table which is the floor of the case body canbe maintained.

As cold air is not introduced into the low temperature zone, decrease incooling efficiency due to frosting can be prevented, and alsodeterioration of accommodated commodities due to the cold air strikingthe commodities can be prevented.

The temperature of the low temperature zone 43 is set to be atemperature range of lower than 3° C. and near 0° C., which is lowerthan toxin producing limit temperature of batulinus and breeding limittemperature of erwinieae, and contact icing or maintaining frozen stateof the accommodated marine products can be performed, thus storagemanagement of marine commodities is possible.

The convection type low temperature zone forming system of the inventioncomprises, as shown in FIGS. 4(A), (B), and (C), a chassis 30 a, anupward-open case body 30 of which the outside wall is covered withinsulation material, a brine chilling unit 30 b provided separately, anda brine piping 30 c. The upward-open case body 30 comprises, as shown inFIG. 4A, a roller conveyer 35 installed in the center part of the floorof the case body 30, cooling flat plate 31 a, 31 a provided adjacent tothe conveyer 35 in both sides thereof, and cooling flat plates 33 a and33 b installed respectively on the laterally longitudinal side walls 33,33 of the case body 30.

The laterally longitudinal side walls 33, 33 are attached by means ofhinges 38 so that they can be turned over in the direction indicated byarrow B (see FIG. 5) and rotary stoppers 39 attached to the side wallscontact the floor of the market to support them when they are turnedover. The shorter side walls 32, 32 of the case body 30 are detachableas shown in FIG. 5(A), and a plurality of low temperature zone formingsystem can be connected as shown in FIG. 5(B).

Each of the cooling flat plates is formed to be a flat tank or thinplate-like containment shell provided with a brine passage within. Eachof the brine piping 30 c is connected to the brine inlet and outlet ofsaid flat tank or thin plate-like containment shell by means of touchconnectors, each connector being provided with automatic shut-offvalves, as shown in FIG. 4(B).

The brine cooled in the brine chilling unit 30 b shown in FIG. 4(B) andin FIG. 5 circulates flowing through the piping 30 c and brine passagesin the cooling flat plates not shown in the drawings to return to thebrine chilling unit in the direction indicated by arrows in FIG. 4(B),the brine piping 30 c is connected at an inlet 37 a and outlet 37 b, forexample, by means of rock coupler plugs.

As the roller conveyer 35 is provided in the center part of the floor ofthe case body 30 along a lateral longitudinal direction as mentionedbefore, commodities such as marine products can be carried into and outof the low temperature zone efficiently and sanitarily by detaching theshorter side walls 32, 32 as mentioned before while preventingcross-contamination, and efficient and sanitary flow of commodities inthe market can be achieved.

When processing of commodities such as cutting of marine products isrequired, the processing is possible by turning or detaching thelaterally longitudinal side wall or walls and bringing out thecommodities carried in on the roller conveyer 35 to the cooling flatplate 31 a, the processing can be done on the cooling flat plate, andthe processed commodities can be auctioned immediately.

Each of the cooling flat plates which can be detached or turned overoutwardly is provided with automatic shut-off valves at the inlet andoutlet for brine, so that the leakage of brine is prevented whendetaching or turning-over the cooling flat plates, and the case body hasenough heat capacity to maintain low temperature of the zone for a whileeven if the cooling flat plates are detached or turned over outwardly.

With the construction described above, it is possible to efficientlycarry in and out commodities and efficiently clean the commodities, thusthe safety management of foodstuffs is made possible.

As said brine is used propylene glycol or salt water, and when saltwater is used, foodstuffs are not damaged by leaked salt water ifleakage occurs.

Example of Test Result

A result of cooling test without placing commodities on the table (noload test) will be explained hereunder.

The dimension of the table of the tested apparatus is 1400×2000 mm.

-   (a) Changes in temperatures over time at positions different in    height from the surface of the table are shown in FIG. 6.

In the graph, each symbol corresponds to the height from the surface ofthe table in the low temperature zone as follows:

-   -   A: 0 mm    -   B: 100 mm    -   C: 200 mm    -   D: 300 mm    -   E: at the position level with the top of the side walls

The temperature of brine was changed in three steps, that was, −1° C.˜1°C., −3° C.˜−1° C., −6° C.˜−3.5° C., as clearly recognized by the curvedenoted by A(the temperature of the surface of the table).

In the graph is also shown the temperature rise when one of the sidewalls was opened after 400 minutes from the start of the test for 7.5minutes and then closed. It is recognized that the temperature wasrestored to low temperature after 16 minutes.

-   (b) Temperature distribution in a horizontal direction after 1.5    hours from the start of the test is shown in FIG. 7.

The temperature of the surface of the table was 0° C. and ambienttemperature was 21.6° C. It is recognized from the graph that the regionlower than 200 mm from the table face was cooled to a temperature lowerthan 12° C. and at 300 mm cooled to 13° C.˜16° C.

It is also recognized that temperatures are highest at the centerpositions remotest from the side walls for cooling air.

-   (c) Temperature distribution in a vertical direction with the    temperature of the cooling flat plate taken as a parameter is shown    in FIG. 8.

Each of thin straight lines B, D, and F in the graph shows distributionof temperature when it is supposed that the temperature rises linearlywith increase in height from the surface of table from the surface to400 mm.

From the graph, it is recognized that actual temperature was higher thanthat of linear distribution at 100 mm, about the same as that of lineardistribution at 200 mm, and lower by about 3° C. than that of lineardistribution at 300 mm from the surface. This is considered to beattributable to the low temperature stratification as shown in FIG. 3.

From the above results, it is recognized that a low temperature zone ofwhich temperature is lower than 10° C. at the positions lower than 200mm from the surface of the table was formed.

-   (d) Heat load(amount of heat taken away by brine) per 1 m² of the    cooling flat plate was calculated as follows:    -   when brine temperature is 0° C.: 504 W/m²,    -   when brine temperature is −2° C.: 540 W/m², and    -   when brine temperature is −5° C.: 576 W/m².

INDUSTRIAL APPLICABILITY

The present invention brings about the following effects by theconstitution described in the forgoing:

-   (a) Low temperature storage of commodities is possible in a    wholesale market in entire process of handling commodities such as    marine products from carrying-in to shipment thereof including    auction in between while maintaining freshness of commodities by    forming on a movable or fixed table a low temperature zone separated    from a contaminated atmosphere.-   (b) Damaging of fishes by cold air involving contaminated outside    air is prevented, since a low temperature zone is formed without    involving outside air.-   (c) In the case of a low temperature zone formed by convection type    thermal stratification, reduction in cooling efficiency due to    frosting does not occur as is often the case with a forced cold-air    circulation type.-   (d) Cooling function can be maintained if the brine piping is    shut-off owing to the large cooling storage capacity of the system.-   (e) A plurality of the system can be connected as necessary so that    carrying-in, auction, and shipment of commodities can be done in a    lump in a wholesale market, resulting in an efficient flow of    commodities in the market, as cooling flat plates each having a flat    heat transfer surface are provided adjacent to a roller conveyer    installed in the center part of the floor of the upward-open case    body which has cooling flat plates each having a flat heat transfer    surface installed on the inside faces of the four side walls    thereof.-   (f) Processing such as cutting of commodities is possible by using    the cooling flat plate having a flat heat transfer surface as a    chopping board.-   (g) Cleaning is easy and safety and sanitary management can be    performed more positively, for the structure is simple and side    walls are detachable or can be turned over outwardly.-   (h) As propylene glycol or salt water is used for the brine for    cooling the cooling flat plates, the foodstuffs are free of    contamination by the leakage of the brine.-   (i) As a touch connector with automatic shut-off valve is used for    connecting brine piping to the cooling flat plate, leakage of brine    when detaching or attaching the side walls can be suppressed to a    minimum.

1. A low temperature zone forming system including an upward-open casebody for displaying commodities, the case body confining a spacesurrounded by a floor face and four side walls, to be used formaintaining freshness of fresh marine products in a wholesale market,wherein a thermally stratified low temperature zone having temperaturedistribution in a vertical direction is formed above said floor face,and further wherein said floor face constitutes a cooling heat exchangerhaving heat transfer faces on both sides thereof, one of the heattransfer faces forming a cooling floor face and the other of the heattransfer faces forming a heat transfer face to perform heat exchange ina cold air producing chamber formed in a rear face side of the floorface, wherein warm air in a warm air zone in an upside opening region ofsaid case body is introduced into said cold air producing chamber to becooled therein, and cold air produced in the chamber is introduced intothe low temperature zone formed above said one of the heat transferfaces to form a new cold air stratified zone.
 2. A low temperature zoneforming system including an upward-open case body for displayingcommodities, the case body confining a space surrounded by a floor faceand four side walls, to be used for maintaining freshness of freshmarine products in a wholesale market, wherein a thermally stratifiedlow temperature zone having temperature distribution in a verticaldirection is formed above said floor face, and cold air is introduced ina lower part of said low temperature zone as necessary at low velocityin an ordinary operation and the introduction of cold air is switched toa forced introduction to form a stratified low temperature zone having arequired temperature distribution in a vertical direction, and furtherwherein said floor face constitutes a heat exchanger comprising acooling flat plate having heat transfer faces on both sides thereof, oneof the heat transfer faces forming a cooling floor face and the other ofthe heat transfer faces forming a heat transfer face to perform heatexchange in a cold air producing chamber formed in a rear face side ofthe floor face, wherein warm air in a warm air zone in an upside openingregion of said case body is introduced into said cold air producingchamber to be cooled therein, and cold air produced in the chamber isintroduced into the low temperature zone formed above said one of theheat transfer faces to form a new cold air stratified zone.
 3. The lowtemperature zone forming system according to claim 2, wherein a separatecooling panel is attached to the rear face of said floor face, the coldair produced by means of the panel is forced into the low temperaturezone above the floor face to form a cold air stratified zone of requiredtemperature.
 4. The low temperature zone forming system according toclaim 1, wherein cold air is introduced in a lower part of said lowtemperature zone as necessary.
 5. The low temperature zone formingsystem according to claim 4, wherein said cold air is introduced at lowvelocity in an ordinary operation and the introduction of cold air isswitched to a forced introduction to form a stratified low temperaturezone having a required temperature distribution in a vertical direction.6. The low temperature zone forming system according to claim 1, whereinsaid floor face is a one-side- cooling flat plate having a flat heattransfer face on one side thereof, and the formation of the thermalstratification is possible in a short time period by concentratingcooling capacity to said heat transfer face.
 7. The low temperature zoneforming system according to claim 1, wherein an inside face of said fourside walls and said floor face are composed to be cooling flat plates,so that a convection type cold air stratified zone is formed by the lowtemperature zone formed by the convection between a descending cold aircurrent produced due to a cooling of air by the cooling plates of thefour side walls and the cold air zone produced due to the cooling of airby the cooling plates of the floor and a hot air region formed abovesaid low temperature zone.
 8. The low temperature zone forming systemaccording to claim 7, wherein cooling flat plates are provided on insidefaces of laterally longitudinal walls among the four side walls.
 9. Alow temperature zone forming system including an upward-open case bodyfor displaying commodities, the case body confining a space surroundedby a floor face and four side walls, to be used for maintainingfreshness of fresh marine products in a wholesale market, wherein athermally stratified low temperature zone having temperaturedistribution in a vertical direction is formed above said floor face,and further wherein a transfer section consisting of a roller conveyeris installed on part of said floor face in a laterally longitudinaldirection or in a crosswise direction, and a cooling flat plate orplates which can serve as chopping boards are provided in a position orpositions other than the transfer section.
 10. The low temperature zoneforming system according to claim 9, wherein the roller conveyer isprovided on said floor face in a laterally longitudinal direction. 11.The low temperature zone forming system according to claim 1, whereinsaid four side walls can be turned over outward or detached, and whenstoring commodities in the case body, the walls are recovered to anerect state with the walls closely contacted with the floor face to beable to again allow the formation of the low temperature zone.
 12. Thelow temperature zone forming system according to claim 1, wherein thetemperature of said low temperature zone can be controlled in atemperature range from storage temperature with ice to a temperature formaintaining a frozen state of marine products by adjusting a coolingtemperature of the cooling heat exchanger or a cooling flat platethrough controlling the temperature of a heat sink for cooling thecooling heat exchanger or the cooling flat plate.
 13. The lowtemperature zone forming system according to claim 1, wherein currentplates are provided at an opening for introducing cold air to the lowtemperature zone.
 14. The low temperature zone forming system accordingto claim 1, wherein a cold air producing chamber which is a shallowpassage formed under the cooling heat exchanger or cooling flat plate ofwhich one of the heat transfer faces forms said floor face and the otherheat transfer face forms a rear face of the floor, and said rear sideheat transfer face is provided with concavities and convexities, fins,or is blast finished.
 15. The low temperature zone forming systemaccording to claim 1, wherein said cooling heat exchanger or coolingflat plate provided to said floor face or to both of said floor face andinside faces of the side walls are supplied with a brine cooled by arefrigerating machine which is housed in a space under the floor face ofthe upward-open case body or the brine cooled by a central refrigeratingmachine which is located outside the system by means of brine piping.16. The low temperature zone forming system according to claim 1,wherein a shut-off valve is attached to a connector fixed to an end ofeach brine piping which is integrated in said cooling heat exchanger orcooling flat plates installed on said floor face or on both of the floorface and the inside faces of said side walls in order that a leakage ofbrine is prevented when detaching or attaching said cooling flat plates.17. The low temperature zone forming system according to claim 1,wherein said upward-open case body is provided with a sunshade sheet toprevent sunlight streams into the low temperature zone.
 18. The lowtemperature zone forming system according to claim 1, wherein saidupward-open case body is provided with casters or the like at its footparts, and a vertical position of the floor face of the case body issuch that putting-on and -down of commodities is easily possible.